JPH0433616B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an injection device for an injection molding machine.

(Prior Art) When a conventional injection device is shown in FIG. 10, raw resin is supplied to a hopper 9 and falls into a cylinder 107, and is heated by a heater (not shown) and rotated by a screw 8 driven by a hydraulic motor 12. It is melted and plasticized, sent to the front of the screw 8, and stored as molten resin 6.

energize the solenoid b of the one-way switching valve 32,
By sending pressure oil from the hydraulic inflow source 31 through the directional switching valve 32 and the proportional electromagnetic flow rate adjustment valve 33 to the head side of the injection cylinder 11, the screw 8 is advanced to the left in the figure through the injection ram 10. The molten resin 6 at the tip is injected from the nozzle 103 into the molded product cavity 22. Note that the hydraulic motor shaft 12
a is spline-coupled inside the injection ram 10,
It is designed to be able to freely slide in the axial direction between the two. In the figure, 1 is a stationary mold, 2 is a movable mold, 13 is a position detection fitting, 14 is a screw position sensor, 34 is an electromagnetic relief valve, 35 is a hydraulic sensor, and 130 is a controller.

However, in the case of this conventional example, as the molten plasticized resin is sent forward of the screw 8, the screw 8 moves back to the right, and the length from the hopper 9 to the tip of the screw 8 gradually becomes shorter. Therefore, the plasticizing effect that the resin supplied from the hopper 9 receives before reaching the tip of the screw 8 changes, and temperature unevenness occurs in the molten resin 6 in the axial direction.

Therefore, when molten resin 6 having temperature unevenness in the axial direction is injected, the temperature of the injected resin also varies depending on the injection stroke position, and changes as shown in FIG. 5, for example. Due to this uneven temperature of the injection resin, the flow state becomes uneven when filling the molded product cavity 22, and also the cooling shrinkage becomes uneven, resulting in flow marks, warpage, etc.
It had drawbacks that caused problems such as distortion and sink marks.

(Problems to be Solved by the Invention) The present invention aims to improve the non-uniformity of the temperature of the injected resin, which could not be avoided with conventional injection equipment, and to dramatically improve the molding quality. .

(Means for Solving the Problems) Therefore, the present invention provides an injection molding machine with a conical hole and a needle pin with a conical tip in the flow direction of the resin passage between the screw tip and the nozzle outlet. A variable conical diaphragm is installed, and when resin is injected, the opening of the variable diaphragm is appropriately changed to control the amount of heat generated by the resin passing through.This is a means to solve the problem. It is something to do.

(Function) The present invention provides a nozzle with a variable conical surface diaphragm consisting of a conical hole and a conical needle pin at the tip,
By changing the aperture amount during injection according to the injection stroke position (or time), the amount of heat generated by the resin passing through the aperture can be controlled, the temperature of the injected resin can be made uniform or change as desired, and the injection stroke direction can be controlled. It is possible to significantly improve defects such as flow marks, warpage, distortion, and sink marks on molded products that occur due to temperature unevenness. In the present invention, the resin flow path is axially symmetrical due to the constriction of the conical surface of the needle pin, and the entire circumference of the conical surface is used, so that the calorific value of the passing resin becomes uniform on the cross-sectional flow surface.

(Example) An example of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of the present invention. Further, details of the nozzle portion shown in Fig. 1 are shown in Fig. 2, details of the needle pin are shown in Fig. 3, and details of the lever are shown in Fig. 4. Now, in Figure 1, 3 is the nozzle, 4 is the needle pin, 5 is the valve body, 7 is the cylinder, 15
is a lever, 16 is a pin, 17 is a connecting fitting, 18 is a hydraulic cylinder, 19 is a trunnion, 20 is a bracket, 21 is a position sensor, 30 is a controller,
36 is a servo valve. In addition, other codes 1,
2,6,8~12,12a,13,14,22,,
Since 31 to 35 are the same as in FIG. 1, the names of the parts are omitted.

Next, in FIG. 2, 3a is a nozzle hole, 3b is a resin passage, 4a is an engaging portion of the needle pin 4 with the lever 15, and 5a is a resin passage, which is a plurality of holes on the circumference. Further, 15a is an engaging portion of the lever 15 with the needle pin 4, 23 is a pin, 24 is a bolt, 25
is the aperture.

Now, in FIG. 2, the valve body 5 is attached to the cylinder 7 with bolts 24, and the nozzle 3 is screwed into the valve body 5. needle pin 4
is slidably fitted into the valve body 5, and has a variable conical surface aperture 25 whose tip is formed by a conical hole formed in the flow direction of the resin passage in the nozzle 3 and a conical portion at the tip of the needle pin 4. , and is connected to the lever 15 at the rear. As shown in FIGS. 3 and 4, the connecting portion between the needle pin 4 and the lever 15 is such that the concave portion 4a of the needle pin 4 and the two prongs 15a of the lever fit together, and the needle pin 4 is moved back and forth in the axial direction by the lever 15. It is now movable. The lever 15 rotates around a pin 23 fixed to the valve body 5.

On the other hand, in FIG. 1, a bracket 20 is attached to the cylinder 7 and rotatably supports the hydraulic cylinder 18 by a trunnion 19. In addition,
The trunnion 19 protrudes to both sides at the longitudinal center of the hydraulic cylinder 18, and is generally used as a trunnion type hydraulic cylinder. Further, the connecting fitting 17 is attached to the rod of the hydraulic cylinder 18, and the lever 15 is connected to the pin 1.
6, and the position sensor 21 detects the stroke position of the hydraulic cylinder 18.

Next, to explain the operation of the embodiment configured as above, in FIG.
By energizing the solenoid b of The molten resin 6 at the tip of the screw 8 is injected into the molded product cavity 22 through the valve body 5 and the resin passage of the nozzle 3.

On the other hand, the pressure oil from the hydraulic inflow source 31 is branched and also communicated with a servo valve 36, which controls the amount of oil to the hydraulic cylinder 18, and therefore flows from the hydraulic cylinder 18 to the connecting fitting 17 and the pin. 16,
The operation of the needle pin 4 is controlled via the lever 15. The opening degree of the diaphragm 25 shown in FIG. 2 changes depending on the position of the needle pin 4. The position of the needle pin 4 is detected by a position sensor 21 that detects the stroke position of the hydraulic cylinder 18 that moves the needle pin 4.
This is done by detecting the Therefore, the position sensor 21 detects the opening degree of the throttle 25 at the tip of the needle pin 4, and the throttle opening degree is feedback-controlled by the servo valve 36.

Now, in FIG. 2, since the resin passage is narrowed by the throttle 25, when the molten resin passes through the throttle 25 during injection, shear heat is generated due to the high-speed flow, and the resin temperature rises. The amount of temperature rise can be freely controlled by changing the opening degree of the throttle 25.

(Effects of the Invention) As mentioned above, resin plasticized with a screw has temperature unevenness depending on the screw stroke position, and if it is directly injected without a restriction as in the present invention, the temperature will change as shown in Fig. 5, for example. . On the other hand, if the opening degree of the aperture shown in Fig. 2 is controlled so as to follow the curve shown in Fig. 8A, the temperature rise of the molten resin passing through the aperture will be as shown in Fig. 8B. By adding the temperature increase shown in FIG. 8 to the resin temperature shown in FIG. 5, a constant injection resin temperature as shown in FIG. 6 can be obtained.

Furthermore, if the temperature of the injected resin is uneven, the flow state will be uneven when filling the molded product cavity, and the cooling shrinkage will also be uneven, resulting in problems such as flow marks, warpage, distortion, and sink marks. In the present invention, a constant injection resin temperature can be obtained, so that the conventional problems can be eliminated.

Also, depending on the molded product, rather than keeping the temperature of the injection resin constant, it is better to change the temperature of the injection resin in accordance with the shape and dimensions of the molded product to reduce the cooling or shear stress of the fluid resin during injection and filling, and the cooling after filling. , may be better from the viewpoint of shrinkage, and even in such cases, the present invention allows the desired injection resin temperature to be freely obtained. For example, if you want the temperature of the injected resin to decrease at a constant gradient as shown in Figure 7, you can inject at the aperture opening as shown in Figure 9 C, and the temperature rise will be as shown in Figure 9 D. All you have to do is get . In Figures 5 to 9, the reference axis (horizontal axis) is the injection stroke (position), but once the injection speed is determined, there is a one-to-one correspondence between the position and time, so the injection stroke (position) ) may be replaced by injection time.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of an injection molding machine showing an embodiment of the present invention, Fig. 2 is an enlarged sectional view of the main parts in Fig. 1, and Figs. 3 and 4 are details of the main parts in Fig. 2, respectively. A perspective view, FIG. 5 is a line diagram showing the relationship between the injection stroke and the injection resin temperature in a conventional injection device, and FIGS. 6 and 7 are lines showing the relationship between the injection stroke and the injection resin temperature in the present invention, respectively. figure,
8 and 9 are diagrams showing the relationship between the injection stroke, throttle opening and temperature rise in the present invention, respectively, and FIG. 10 is a circuit diagram of a conventional injection molding machine. Explanation of main parts of the figure 3... Nozzle, 3a... Nozzle hole, 3b... Resin passage, 4... Needle pin, 5...
Valve body, 7...Cylinder, 8...Screw, 15
...Lever, 18...Hydraulic cylinder, 25...Aperture (variable aperture).

Claims (1)

[Claims] 1. In an injection molding machine, a variable conical surface orifice consisting of a conical hole and a needle pin with a conical tip is provided in the flow direction of the resin passage between the screw tip and the nozzle outlet, and the variable conical surface throttle is provided when injecting the resin. An injection device characterized by controlling the amount of heat generated by passing resin by appropriately changing the opening degree of the aperture.